There always are clever people doing clever things with mobile phones, and one of the most clever is to tap into the Internet to avoid long distance charges.

The mobile VoIP sector, which has languished to a certain extent -- perhaps because some of the procedures are confusing -- is heating up. BusinessWeek does a good job of summing up the situation from the consumer point of view. The bottom line is that a lot of providers -- including Jajah, iCall, Gorilla and Truphone -- are lining up to serve customers. At the same time, the piece does a good job of describing the confusion. In addition to the fact that there is more than one way to provide service, device manufacturers and carriers aren't totally ambivalent.

This week, it should be noted, Half Life Source reported that Skype, the most recognizable provider of third-party VoIP phone software, has begun beta testing Java-based version of its mobile software.

The use of cell to make VoIP calls makes too much sense not to find wide use. The story cites several analysts' reports. ON World says that last year there were 7 million people making mobile VoIP calls. That number will grow to 100 million by 2011. Gartner's take is that 5.5 percent of mobile phones sold this year were Wi-Fi-enabled. That number will reach 33 percent. Finally, Insight Research says 24 percent of the 1.2 billion wireless minutes sold this year will be used for VoIP calls.

One key is how much VoIP functionality comes with the phone and how much is added later by third parties. The highly sensitive nature of the intersection of handsets and software developers is apparent in this GigaOm post that surmises that Nokia, after initially including mobile VoIP on its phones, appears to be at least partially backing away. The new N78, for instance, doesn't have VoIP capabilities, though VoIP works on some E-series phones. The writer surmises that mobile VoIP has been spared in the E-series because the phones are used more by enterprises that want voice over wireless local-area network (VoWLAN) functionality.

The complexity of this new world is apparent in the description offered in a press release trumpeting a study by Research and Markets. The firm says that the number of voice over 3G users could reach 250 million by the end of 2012 from zero at the beginning of last year. This group is distinct from and a larger than those who using dual-mode VoWLAN phones. The report positions VoIP over 3G as a bridge technology to all-IP platforms such as Long Term Evolution and Ultra Mobile Broadband (LTE and UMB). The list of conclusions offered in the release make one thing clear: This is a confusing arena that features a variety of technologies and topologies.

Mobile VoIP is becoming more common for international calls. The basic approach is similar to domestic mobile VoIP. The savings, of course, can be greater. The pros, as outlined in a graphic in this Wall Street Journal piece, are cheap flat rates and freedom of choice in selection of the network and device. The biggest negative is dicey call quality. Another graphic at the end of the story provides contact information, sample pricing and miscellaneous comments on Jajah, Rebtel, Maxroam, Truphone and MyGlobalTalk, which is expected to launch next month.